1. Field of the Invention
The present invention relates to a reformer for reforming a supply of hydrocarbon to generate a hydrogen rich gas, and also to a fuel cell system with such a reformer.
2. Description of the Related Art
During non-operation of a fuel cell, the fuel cell and a reformer are kept in the environment different from that during operation of the fuel cell. In known fuel cell systems, the gaseous fuel remaining in the reformer and the fuel cell is replaced with an inert gas fed into the fuel cell system while the fuel cell stops operation. The replacement with an inert gas interferes with an unrequired progress of electrochemical reactions with the residual gaseous fuel and prevents generation of water in a cathode of the fuel cell, thereby preventing dew condensation in the electrodes or a pathway for gas flow and corrosion of electrodes by water. The replacement also prevents the fuel cell system including a reformer, a fuel cell, and a piping system from being affected by the negative pressure. For examples, the replacement protects an electrolyte membrane, such as a polymer electrolyte membrane, from damage by the negative pressure or prevents deterioration of the electrocatalytic ability by the air flown into the system.
A variety of methods including one with a tank of inert gas are applicable to replacement with an inert gas. A technique proposed and disclosed in JAPANESE PATENT LAYING-OPEN GAZETTE No. H2-117071 separates the air into oxygen and nitrogen and introduces the nitrogen to the fuel cell system.
The proposed technique does not require time-consuming replacement of a gas tank, but requires a specific mechanism for removal of oxygen from the air and a reservoir for storing gaseous nitrogen, thereby making the whole system rather bulky.